1. Field of the Invention
The invention relates to a neutral electrode for a High-Frequency (HF) surgical instrument.
2. Background of the Invention
A neutral electrode of the kind mentioned above, which operates with two planar partial electrodes, is known, for example, from German utility model No. 82 05 363. In this type of neutral electrode, monitoring of the electrically conducting connection with the patient is carried out by a control circuit having a low frequency control current. The control current flows from the contact surface of one partial electrode, through the skin of the patient, to the contact surface of another partial electrode. A similar two-part neutral electrode is known from German patent publication No. DE-A-28 49 422.
Consequently, multi-part electrodes permit determining with greater certainty whether the particular neutral electrode of the HF surgical instrument is in contact with the patient over a sufficiently large area or not. A monitor or safety circuit with which the contact of a three-part neutral electrode in the field of HF surgery can be monitored is known, for example, from FIG. 4 of U.S. patent application Ser. No. 929,561, filed Nov. 10, 1986.
A problem in constructing a multi-part electrode deals with finding a configuration which largely avoids a possible nonsymmetrical distribution of the high frequency energy emitted by the active electrode to the partial electrodes of the neutral electrode.
By using a two-part electrode, spurious measurements during the process of monitoring can occur. This can be of particular significance if the neutral electrode is fastened on an extremity of a patient, such as an arm or a leg. In particular, nonsymmetrical distribution of the high frequency energy being emitted by the active electrode over the partial electrodes of the neutral electrode can be brought about, which should be avoided.
Hence, it is an object of the invention to develop an electrode of the above mentioned kind in such a way, that uniform distribution of the high-frequency energy over its partial electrodes is ensured, in particular even when the electrode is applied on an extremity of the patient.